Dry etched nanoporous silicon substrates for optical biosensors

Porous silicon is an attractive platform for the encapsulation of chemical and biological recognition elements. We demonstrate fabrication of porous silicon using a dry etching technique. The Xenon Difluoride etching technique allows selective formation of porous silicon with a standard photoresist layer as mask. We demonstrate free standing 5μm thick porous silicon films for biological sample filtering. Further, we employ the porous silicon as a substrate for the immobilization of xerogel thin films that encapsulate specific analyte responsive luminophores in their pores. The porous silicon behaves as an optical interference filter which allows selective enhancement of the wavelengths of interest.